Switchgear unit for a consumer, especially a motor starter

ABSTRACT

The Switchgear unit, especially a motor starter, has a contactor and a power switch for short-circuit protection. The additional function of overload protection envisaged for the switchgear unit is integrated in an overload relay that is configured separately from the power switch. The components thereof extend into free areas formed by the arrangement of the contactor and power switch as standard components on a support.

This application is the national phase under 35 U.S.C. § 371 of PCTInternational Application No. PCT/DE02/01282 which has an Internationalfiling date of Apr. 8, 2002, which designated the United States ofAmerica and which claims priority on German Patent Application number DE101 19 458.7 filed Apr. 20, 2001, the entire contents of which arehereby incorporated herein by reference.

FIELD OF THE INVENTION

The present invention generally relates to a switchgear unit for a load,in particular a motor starter, having a switching unit for switching theload during operation, and having the functions of short circuitprotection and overload protection.

BACKGROUND OF THE INVENTION

A switchgear unit is generally also referred to as a load feeder and isusually arranged in a switchgear cabinet on a standardized top-hat railnext to other load feeders. The load feeders arranged in a switchgearcabinet are assembled in a modular fashion in order to make it possibleto meet the respective requirements. Load feeders of this type areprovided in particular in industrial systems for controlling andswitching high currents and voltages. The switchgear unit is used inparticular to drive a three-phase motor. The switchgear unit is in thiscase also referred to as a motor starter.

The switchgear unit of a motor starter generally has three functions forprotecting the motor. The first function is that of switching the motorduring operation, and is performed by a dedicated standard unit, usuallya so-called contactor. The contactor is designed to repeatedly switchhigh currents on and off, during operation. Furthermore, in a switchgearunit, the functions of short circuit protection and overload protectionare integrated in a standard unit referred to as a power breaker. Thepower breaker isolates the load from the power supply system when ashort circuit occurs and also when the current is too high. The twostandard units are arranged next to one another on a common carrier andform the switchgear unit.

DE 43 35 965 discloses a motor starter having integrated short circuitprotection and in which a power breaker, an electronic tripping unit anda contactor are arranged one behind the other. The electronic trippingunit is integrated together with the power breaker in a commonenclosure. The tripping unit in this case has a release which providesthe thermal overload protection for the motor.

FR 2 003 575 discloses a contactor having a short circuit release whichis provided as an attachment and having an attachment which contains athermal overcurrent release.

WO 99/23737 discloses a switchgear unit which has a contactor and apower breaker, each as separate units. These units are arranged on asubcarrier in which a printed circuit board with electronics isintegrated. Such electronics make it possible to drive the switchgearunit by way of a bus system. In this case, in particular two bus systemsare provided, that is a data bus for interchanging signals and a powerbus for supplying power. As an alternative to the standard units of thecontactor and the power breaker, an electronic circuit is proposed whichis, however, less suitable for switching very high currents than theelectromechanical units of the contactor and the power breaker, or isvery complex and expensive.

SUMMARY OF THE INVENTION

An object of the present invention is to specify a cost-effectiveswitchgear unit where design is as simple as possible.

An object of the present invention is achieved by providing a switchgearunit, in particular for a motor starter, having the functions ofswitching, short circuit protection and overload protection duringoperation, provision is made for each of these functions to be performedin a separate functional unit. The switching operation is in this casemay be performed by a switching unit, in particular a contactor. Thefunction of short circuit protection may be performed by a powerbreaker, and the function of overload protection may be performed by anoverload relay which is separate from the power breaker.

The functions of overload protection and short circuit protection areusually integrated in a conventional power breaker. In order to ensurethat the functions of short circuit protection and overload protectionare reliably performed, the power breaker must be specifically designedfor the switching current envisaged in each case. Switching current isregarded here as the current for which the switchgear unit is designed.This means that, for example, for the switching current range between 0and 25 A, approximately twenty separate, differently designed powerbreakers are required. This results in considerable cost and requiressignificant care to be taken when selecting the appropriate powerbreaker.

By separating the functions of short circuit protection and overloadprotection, the switchgear unit may be considerably simplified. Inparticular, the function of overload protection no longer needs to beintegrated in the power breaker, which can primarily be designed for thefunction of short circuit protection. The power breaker as a result hasa much simpler design and is thus more cost-effective, and can also beused over a broad current range. The function of overload protectionperformed in the overload relay is also comparatively simple as a resultof it being separate from the short circuit protection.

The overload relay may be in the form of an electronic overload relaywhich has, in particular, a current transformer. This currenttransformer is arranged around a conductor to be monitored in the mannerof a current measuring coil, and detects the magnetic field induced bythe conductor through which current is flowing. An electronic evaluationunit connected to the current transformer determines from this thecurrent flowing through the conductor. Based on this principle, theelectronic overload relay can be used for a very broad current range.The electronics determine the current level above which the overloadrelay will trip, and this current level can be almost any desired value.

In order to allow for a switchgear unit design which is ascost-effective and compact as possible, the switching unit and the powerbreaker may be designed as standard components which are arranged on acarrier so as to form a free space. At least one component of theoverload relay extends into this free space. This makes it possible tokeep the physical space required for the switchgear unit small, whichmeans that there is a small space requirement in the switching cabinetand the installation costs are low.

Of particular advantage for cost-effective design is the use of standardunits for the switching unit (contactor) and the power breaker. Suchstandard units usually have a cutout underneath for mounting them on atop-hat rail, and this cutout forms a free space in which the componentpreferably engages. In addition, an interspace is usually providedbetween the contactor and the power breaker and likewise advantageouslyacts as a free space for arranging a component of the overload relay.

In an expedient manner, in this case, the current transformer inparticular extends into the free space, since it takes up the mostphysical space owing to its coil structure. A dedicated currenttransformer is provided in the overload relay for each phase of thepower supply system. These current transformers are thus arranged suchthat they are distributed, for example, in the two cutouts or in theinterspace.

In an expedient manner, for a compact arrangement, the component, whichextends into the free spaces, is arranged on the carrier on which thecontactor and the power breaker are also mounted.

In a particularly expedient refinement, provision is made for thecomponents of the overload relay to be arranged on a printed circuitboard on the carrier. The printed circuit board is preferably at thesame time fitted with bus electronics so that the switchgear unit isdesigned for connection to a bus system. By integrating the electronicoverload relay on the printed circuit board, the space requirement isminimized in a particularly efficient manner, and the production costsare kept low. This is because the printed circuit board which is usuallyused for bus electronics nowadays needs only a few additional electronicfunctions for modern switchgear units. Owing to the high degree ofautomation in the production of printed circuit boards, this requiresonly a little additional complexity. However, considerable savings canbe made since, on the one hand, the power breaker can be designed in asimplified fashion without the function of overload protection, and canbe used in the standard way for a broad current range. At the same time,on the other hand, by integrating the electronic overload relay on theprinted circuit board with the current transformers extending into thefree spaces, a very small physical volume is achieved which also keepsthe costs of installing the switchgear unit low.

Further scope of applicability of the present invention will becomeapparent from the detailed description given hereinafter. However, itshould be understood that the detailed description and specificexamples, while indicating exemplary embodiments of the presentinvention, are given by way of illustration only, since various changesand modifications within the spirit and scope of the invention willbecome apparent to those skilled in the art from this detaileddescription.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description given hereinbelow and the accompanying drawingwhich IS given by way of illustration only, and thus are not limitativeof the present invention, and wherein:

The single FIGURE illustrates a simplified schematic and perspectiveillustration of a switchgear unit.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

The switchgear unit 2 has a contactor 4, in the form of a standard unit,as a switching unit for the function of switching during operation.Furthermore, a power breaker 6 is likewise provided as a standard unitfor the function of short circuit protection. The contactor 4 and thepower breaker 6 intended to be arranged on an approximately L-shapedcarrier 8. The carrier 8 is usually intended to be snapped or pushedonto a top-hat rail in a switchgear cabinet.

A printed circuit board 10 is integrated in the base of the carrier 8and is fitted with a number of electronic components 12 andcontact-making devices 14. In particular, bus electronics are integratedon the printed circuit board 10 such that the switchgear unit 2 can beconnected to a bus system. This bus system is, for example, a signal busfor transmitting signals and/or a power bus for supplying power to theswitchgear unit 2.

The present invention also provides for the function of overloadprotection to be performed separately from the power breaker 6. For thispurpose, the function of overload protection is performed by anelectronic overload relay which has, in particular, a currenttransformer 16 for each phase conductor of the power supply system.Associated with the electronic overload relay are, furthermore, some ofthe components 12 arranged on the printed circuit board 10. The currenttransformer 16 is in the form of a current measuring coil and serves thepurpose of detecting the magnetic field induced by the phase conductorthrough which current is flowing. The respective current levels aredetermined from the signals from the current transformer 16 by means ofthe components 12.

Owing to the use of standard units for the contactor 4 and the powerbreaker 6, they each have a cutout 18 underneath for arranging them on atop-hat rail. When the contactor 4 and the power breakers 6 are arrangedon the carrier 8, the configuration results in an interspace 20 beingformed between these units. The cutouts 18 and the interspace 20 formfree spaces by virtue of this configuration.

In order to make expedient use of these free spaces that are present,the current transformers 16 extend into these free spaces. In theexemplary embodiment, two current transformers 16 are shown which extendinto the cutout 18 in the power breaker 6. As an alternative to this,the current transformers can also be arranged distributed over the twocutouts 18 and the interspace 20, or arranged exclusively in theinterspace 20 or exclusively in the cutout 18 in the contactor 4.

Owing to the use of the free spaces formed by virtue of theconfiguration, the space requirement for the switchgear unit 2 is keptvery small, overall. This achieves a compact physical volume and keepsthe space requirement in the switchgear cabinet small, and thus theinstallation costs low. In addition, simplification of the power breakeris made possible by integrating the function of overload protection in aunit which is separate from the power breaker 6, the electronic overloadrelay.

Exemplary embodiments being thus described, it will be obvious that thesame may be varied in many ways. Such variations are not to be regardedas a departure from the spirit and scope of the present invention, andall such modifications as would be obvious to one skilled in the art areintended to be included within the scope of the following claims.

1. A switchgear unit, comprising: a switching unit for switching a loadduring operation thereof, the switching unit including short circuitprotection and overload protection functionality, the function of shortcircuit protection being integrated in a power breaker, and the functionof overload protection being integrated in a separate functional unit inan electronic overload relay which is separate from the power breaker,wherein the switching unit and the power breaker are arranged on acarrier so as to form a free space, at least one of components of theoverload relay extending into the free space.
 2. The switchgear unit asclaimed in claim 1, wherein the overload relay is in the form of anelectronic overload relay.
 3. The switchgear unit as claimed in claim 1,wherein the power breaker and the switching unit each have a cutout onan underside thereof, the cutouts being for mounting the power breakerand the switching unit on a top-hat rail, and the component beingcapable of engaging at least one of the cutouts.
 4. The switchgear unitas claimed in claim 1, wherein the power breaker and the switching unitare arranged next to one another so as to form an interspace, theinterspace capable of accommodating the component or a plurality ofcomponents.
 5. The switchgear unit as claimed in claim 1, wherein theoverload relay has a current transformer which extends into the freespace.
 6. The switchgear unit claimed in claim 1, wherein a component ofthe overload relay is arranged on the carrier.
 7. The switchgear unit asclaimed in claim 1, wherein components of the overload relay arearranged on a printed circuit board on the carrier.
 8. The switchgearunit as claimed in claim 7, wherein the printed circuit board is fittedwith an electronic bus system.
 9. The switchgear unit as claimed inclaim 3, wherein the power breaker and the switching unit are arrangednext to one another so as to form an interspace, the interspace capableof accommodating the component or a plurality of components.
 10. Theswitchgear unit as claimed in claim 3, wherein the overload relay has acurrent transformer which extends into the free space.
 11. Theswitchgear unit as claimed in claim 4, wherein the overload relay has acurrent transformer which extends into the free space.
 12. Theswitchgear unit claimed in claim 3, wherein a component of the overloadrelay is arranged on the carrier.
 13. The switchgear unit claimed inclaim 4, wherein a component of the overload relay is arranged on thecarrier.
 14. The switchgear unit claimed in claim 5, wherein a componentof the overload relay is arranged on the carrier.
 15. The switchgearunit as claimed in claim 3, wherein the components of the overload relayare arranged on a printed circuit board on the carrier.
 16. Theswitchgear unit as claimed in claim 4, wherein the components of theoverload relay are arranged on a printed circuit board on the carrier.17. The switchgear unit as claimed in claim 5, wherein the components ofthe overload relay are arranged on a printed circuit board on thecarrier.
 18. The switchgear unit as claimed in claim 6, wherein thecomponents of the overload relay are arranged on a printed circuit boardon the carrier.
 19. A switchgear unit, comprising: a switching unit forswitching a load during operation thereof, the switching unit includingshort circuit protection and overload protection functionality, thefunction of short circuit protection being integrated in a powerbreaker, and the function of overload protection being integrated in aseparate functional unit in an electronic overload relay which isseparate from the power breaker, wherein the load is a motor starter.20. The switchgear unit as claimed in claim 19, wherein the powerbreaker and the switching unit each have a cutout on an undersidethereof, the cutouts being for mounting the power breaker and theswitching unit on a top-hat rail, and the component being capable ofengaging at least one of the cutouts.
 21. An apparatus, comprising: amountable power breaker having integrated short circuit protectionfunctionality; and overload protection circuitry being functionallyseparate from the power breaker, the overload protection circuitry beingposition in a free space defined at least in part by the power breaker.22. The apparatus according to claim 21, wherein the over loadprotection circuitry includes at least an electronic overload relay. 23.The apparatus according to claim 21, wherein the free space defined atleast in part by the power breaker is defined by an underside thereof.24. The apparatus according to claim 21, wherein the power breaker ismounted on a carrier, the power breaker and carrier combination therebydefining a switchgear unit.